Conventional surgical interventions performed in interventional radiology, without any navigation system, consist in introducing a tool, such as a needle or equivalent, in the body of the patient. The interventional radiologist uses an imaging system, most likely a Computed Tomography Scan (CT-Scan) or a Magnetic Resonance Imaging system (MRI), to see the organs of the patient and choose the target for the tip and trajectory of the needle.
In order to help the interventional radiologist to reach the target, a navigation system is necessary. Such systems have been developed for neurosurgical interventions for example. Those systems use a localizing system, also called tracking system, based on optical, electromagnetic, radiofrequency, acoustic (sonar) or mechanical technology. The objective of the localizing system is to give the spatial position and orientation in real time of one or more trackers. The tracker position and orientation is given relatively to the localizing system itself or relatively to another tracker.
An example of such localizing system is based on the electromagnetic technology. More precisely the localizing system comprises an emitter which emits a magnetic field generated by coils, and a tracker operating as a receiver which measures the magnetic field around itself when positioned in the emitted magnetic field. Those measures are sent to a computer system that calculates the position and orientation between the emitter and the trackers (receivers). Those magnetic systems are very ergonomics and easy to use because no direct visualization is required, such that some obstacles may be positioned between the emitter and the tracker (a hand, a surgical drape for example) without any impact on the accuracy of the measurement. One of those magnetic systems is for instance the Aurora device produced by Northern Digital Inc. (Waterloo, Ontario, Canada) or the Patriot device produce by Pohemus Inc. (Colchester, Vt., USA). However, the measurement precision is better when the distance between magnetic emitter and magnetic tracker is as small as possible.
Some navigation systems using magnetic localizer technology have been developed and used to track the tip of needles in CT images, during an intervention performed inside the CT room directly. One of those systems is for instance the device produced by Traxtall (Ontario, Canada). However, those systems have two major drawbacks. First, they are not always accurate, particularly when the distance between the tip of the needle and the magnetic emitter is not small compared to the distance between the tip of the needle and the metallic table that generates artefacts. Inaccuracy can reach more than 5 millimetres which is not acceptable. Further, the existing systems are complex to use and need user interaction.
The object of the present invention is to provide a method and device for navigating a tool which solve at least one of the drawbacks mentioned above.
In particular, an object of the invention is to provide a method and device for navigating a tool which is very precise, and at the same time enable the practitioner to intervene quickly on the patient.
Another object of the invention is to provide a method and device for navigating a tool which may be fully automatically operated, without requiring any particular action from the practitioner.